The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
With the popularity of digital cameras, it becomes much easier for people to take pictures. However, organizing a large number of pictures is hard. As a result, many people have thousands of photos sitting on their hard disk in some miscellaneous folder. Annotating images with tags is an effective way to organize images. Manual annotation is time consuming, while automatic approaches are not always reliable due to the semantic gap between low level visual features and high level semantic concepts.